SEM Photography and Science Photos | Articles by PSmicrographs

About Scanning Electron Microscopes (SEM)

Survival Against All Odds

It was the summer of 2009 and we were in the garden and as most most people know, cabbage white butterfly eggs on the leaves of your Brassicas is a gardener’s nightmare.  When hatched into caterpillars, these veracious eaters will devour your cabbages before you can say meat and veg (less cabbage).  Having these tiny eggs in our garden and being in possession of a scanning electron microscope (in the lounge would you believe), we decided that some of these eggs could be sacrificed in the name of science.   

This exercise is rather time consuming as the eggs have to be carefully handled and prepared so they can stand the rigors of the vacuum chamber of the electron microscope.  After carefully removing the eggs from the brassica leaf they were placed in Osmium Tetroxide vapour for ½ hour.  This is a highly toxic substance which makes tissue go black and fixes proteins.  The next process is to coat the eggs in gold to make them conductive so they don’t “charge” in the electron microscope.  This process is called “sputter coating” which has to be done under vacuum in a sputter coater machine. Charging will ruin an image and damage the sample so sputter coating of tissue is a must for electron microscopy.

After 5 hours, the electron microscope was brought back to atmospheric pressure and the eggs were removed and left on the side.  Next morning we noticed something moving, the eggs were starting to hatch.  8 of the caterpillars survived.  They were put onto nasturtians as a food plant but 5 subsequently died after a few days.  The remaining 3 carried on to pupate and in the following spring (March) all 3 emerged from the chrysalis, apparently fit and well as you can see by the 3 time lapse videos on this site.